NIST Standard Reference Database 35

NIST/EPA Gas-Phase Infrared Database JCAMP Format

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This data collection contains 5,228 infrared spectra of different compounds along with chemical structures for most of them. Spectra are provided on a CD-ROM in the JCAMP-DX (Joint Committee for Atomic and Molecular Physical Data "Data Exchange") format. Chemical structures are provided in the MOL-file format. The IR data originated from two sources, from the so-called "EPA Vapor-Phase IR Library" and from NIST laboratories. The data have been sub-divided in two ways: 1) as concatenated JCAMP and SDF files (concatenated MOL-files) and 2) in individual files where each spectrum and structure is provided in a separate JCAMP and MOL file, using file names containing the CAS registry number of the compound.

The data originally derived from the EPA Vapor-Phase IR Library itself (3,108 spectra) and the spectra measured at NIST (2,120 spectra) are provided in separate directories. All spectra are given as normalized absorbance and empirical formulas and CAS Registry Numbers are given for all compounds. About 80% of these compounds (and nearly all in the NIST collection) have mass spectra included in the NIST/EPA/NIH Mass Spectral Database.

The EPA-IR collection has already been widely distributed and now exists in a number of differently edited versions on a variety of commercial data systems. The original EPA-IR collection contained 3,300 spectra measured by GC-IR under EPA contract. These were obtained at 4 cm-1 resolution from 450 to 4000 cm-1, although values below 500 cm-1 and above 3900 cm-1 often show extraneous signals. The sequence number of each spectrum in the original EPA-IR Database is provided. Each spectrum was inspected at NIST and, where possible, compared to published spectra or to spectra generated at NIST. 145 erroneous or low quality spectra were excluded and 47 spectra were replaced by spectra of higher quality obtained at NIST. A complete original set of "header" information has not been located, so analytical conditions are not given. Further, we cannot be certain of the correctness of the absolute values of absorbance.

NIST spectra were obtained on an integrated capillary GC-MS-IR instrument at 8 cm-1 resolution, most between 550 and 4,000 cm-1. Maximum percent transmittance generally fell between 85% and 96%. Approximately 400 spectra present in the EPA file were remeasured at NIST; agreement was excellent in all cases. When spectra were equivalent in quality, the EPA spectrum was selected for inclusion. In all cases where a single GC run generated acceptable IR and Mass Spectra, the identification number (NIST/EPA spectrum number) of the compound in the NIST/EPA/NIH Mass Spectral Database was assigned.

Spectra included in the NIST/EPA IR data file have been baseline corrected using a single algorithm for all spectra and all have been converted to exact 8.0 cm-1 resolution. This was done to ensure homogeneity of the data. EPA spectra are given in the range 450 - 3966 cm-1, and NIST spectra were acquired from 550 - 3846 cm-1.

It is important to note that this data cannot be used for quantitative purposes since measurements by GC/IR do not provide molar absorbance values. They are intended for use in compound identification as a source of relative absorbance information at different wavelengths for a given substance. Note also the gas phase spectra contained in this collection are generally quite different than condensed phase spectra.

You may browse the Users' Guide to see how this works.

Important Note: All spectra were measured in the gas phase by GC/IR (gas chromatography/infrared spectroscopy), hence concentrations in the IR cell are not known or estimable. Molar absorption coefficients are not reported. This data provides only relative absorption coefficients as a function of wavelength which can be used for identification, not quantification.

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For more information please contact:
Standard Reference Data Program
National Institute of Standards and Technology
100 Bureau Dr., Stop 6410
Gaithersburg, MD 20899-6410
(844) 374-0183 (Toll Free)/(301) 975-4553 (FAX)

The scientific contact for this database is:
Stephen E. Stein
Mass Spectrometry Data Center
National Institute of Standards and Technology
Gaithersburg, MD 20899-8380 (301) 975-2505 steve.stein [at] nist.gov (steve[dot]stein[at]nist[dot]gov)

Keywords: EPA, gas-phase, infrared spectra, spectra, mass spectra, IR, JCAMP, vapor-phase IR, NIST, critically evaluated data, CAS number, formula, chemical structures, chemistry, molecular spectroscopy, molecular vibration, spectroscopy.

data [at] nist.gov (Customer Support)